1. Field of the Invention
The present invention relates, generally, to a dye that can function as a dispersant and a solar cell comprising the dye. In one embodiment, the dye comprises a dispersant functional group so as to simultaneously exhibit a dye function and a dispersant function.
2. Description of the Related Art
A dye-sensitized solar cell is a photoelectrochemical solar cell composed mainly of a photosensitive dye molecule for absorbing visible light to produce electron-hole pairs, and transition metal oxide for transferring the produced electrons.
Such a dye-sensitized solar cell consists of a semiconductor electrode, an electrolyte, and a counter electrode, in which the semiconductor electrode includes a conductive transparent substrate and a light absorbing layer including a metal oxide and a dye.
The semiconductor electrode is obtained by forming a metal oxide film on a substrate and then adsorbing a dye on the film. Specifically, a paste composition of metal oxide is applied on a transparent substrate and then burned at a high temperature of about 400 to about 550° C. to form a metal oxide film, which is then immersed in a dye-dissolved solution for a predetermined period of time to adsorb the dye on the surface of the film.
In this way, in the formation of the semiconductor electrode of a dye-sensitized solar cell, since the metal oxide film is formed on the substrate and then the dye is adsorbed on the film, it is difficult to use the entire surface area of the metal oxide particles, thus causing a problem in which the adsorbed amount of dye is very small relative to the optical cross-section of light. When the amount of dye adsorbed is small, the photoelectric efficiency of the solar cell is decreased.
Further, in the case where the metal oxide film is formed using nanoparticles, agglomeration of the nanoparticles in the paste may occur, thereby undesirably reducing the uniformity and density of the metal oxide film, leading to decreased photoelectric efficiency of the solar cell.
In this regard, Korean Patent Laid-open Publication No. 2005-82624 discloses a dye-sensitized solar cell manufactured by forming a porous film of metal oxide through an electrochemical process using a surfactant and then adsorbing a dye thereon, so as to increase the photoelectric efficiency of the solar cell. In addition, Japanese Patent Laid-open Publication No. 2002-50413 discloses a dye-sensitized solar cell, which comprises a photosemiconductor layer composed of porous photosemiconductor particles obtained by burning photosemiconductor powder in the presence of a surfactant or a hydrophilic polymer compound and a dispersion medium at a temperature of 400° C. or higher and then milling it.
According to such conventional techniques, in which the surfactant or dispersant is to the metal oxide film, the porous properties of the metal oxide or photosemiconductor particles are enhanced by the introduction of the surfactant, therefore slightly increasing the adsorbed amount of dye and the uniformity of the metal oxide film. However, since the dye adsorption process is usually performed after the formation of the metal oxide film or semiconductor layer, it is difficult to use the entire surface area of the metal oxide particles, and consequently it is impossible to sufficiently increase the adsorbed amount of dye and the photoelectric efficiency.